The known ground support systems comprise a intermittent combustion engine, a generator to supply electrical power, and an air pump to supply pressurised air. The intermittent combustion engine is an internal combustion engine and is sometimes also referred to as a reciprocating combustion engine. In general a diesel four stroke engine is used, but also other intermittent combustion engines may be used. The generator and air pump are operatively coupled to the combustion engine. In use, the combustion engine runs at a predetermined rotational speed. This is required because the electrical power supplied by the generator needs to have a constant frequency. As a result of this, the pressurised air supplied by the air pump has a constant air flow rate. The pressurised air is used to test the aircraft, more specifically the equipment of the aircraft. The air pump continuously produces its maximum air flow rate. If at a certain moment a lower air flow rate is required, the pressurised air supplied by the air pump is partly discharged. This also means that the combustion engine continuously operates at its maximum. The invention is based on the insight that there is a need in the field of the art that a ground support system can provide multiple tasks.